This invention relates to a power plant integrated with coal gasification and with a gas turbine plant using a combustible gas produced from the coal gasification as a fuel, and provides a power plant integrated with an apparatus for coal gasification, which produces a combustible gas by reaction of coal with a gasifying agent containing at least oxygen as an effective component.
Coal gasification has, for example, been actually utilized in a power plant integrated with coal gasification, etc, with being oxygen or highly oxygen-enriched air is supplied to a coal gasification plant as a gasifying agent. However, consumption of the generated electric power in an auxiliary facility including an oxygen plant for producing such a gasifying agent is too large to maintain a good energy efficiency of the entire power plant, as will be become more apparent from the following description.
As shown in FIG. 1, a gasification plant 10 is integrated with a power plant 30 including a gas turbine using a combustible gas produced from the gasification plant 10 as a fuel, with the gasification plant 10 comprising a gasification furnace 11 which produces a combustible gas 2 by reaction of coal 1 with oxygen 8 as a gasifying agent together with steam 4, etc., and a cooler 12 which cools the combustible gas 2 produced in the gasification furnace 11. The combustible gas 2 thus formed is subjected to dust removal and sulfur removal in a gas purification plant 20 to obtain a fuel gas 3 for gas turbine. In the prior art, an oxygen plant 40 is used as an apparatus for supplying a gasifying agent, and produces highly oxygen-enriched air as a gasifying agent. Thus, the oxygen plant 40 must be designed to meet a desired oxygen concentration. For example, it can produce oxygen 8 with a 98% oxygen concentration, the balance being air. The oxygen plant 40 comprises a feed air compressor 41, an air separator 42 for separating oxygen from air, and an oxygen compressor for compressing the oxygen from the air separator 42. The nitrogen separated from air is utilized in other places as a by-product from the oxygen plant 40.
In addition to the oxygen plant 40, there are an air compressor 50 and a mixing drum 54 to mix the oxygen 8 with air to obtain an oxygen-enriched air 9 with a desired oxygen concentration, which is supplied to the gasification plant 10.
In the prior art construction of FIG. 1, the oxygen plant 40 consumes a considerable amount of electric power, and usually, about 13% of electric power generated in the power plant 30 is consumed in the oxygen plant 40. In the case of thermal electric power generation by firing heavy oil, etc., about 5% of the generated electric power is consumed in the auxiliary facility, and in the case of thermal electric power generation by direct firing of coal as fuel, about 8% of the generated electric power is consumed. Thus, the power consumption in the auxiliary facility is considerably larger in the thermal electric power generation using the coal gasification fuel than in the other cases, because about 15% of the generated electric power is consumed in the entire plant. Thus, it is an important task in the art of coal gasification to reduce consumption of the generated electric power in the auxiliary facility to thereby improve the energy efficiency of the entire power plant.